The concept is pretty much a tiny rocket motor to light the larger one!

I used GOX and Propane ignited by the sparkplug, I had a few issues though which as you can see in the video looks like more a series of little explosions rather than sustained igniton.My fuel/ox oriffice sizing was too big and was blowing out the fire, so to speak,so would only ignite when the sparkplug fired, I think the impingment might have been abit off as well, and my sparkplug was not pulsing enough, I had it hooked up to an electric fence unit, was abit slow. So next test, smaller oriffices, faster pulse and see what happens!If not I got another design which I'll machine up over the weekend which should work for sure anyhow!!

The entire thing is made from a solid bit of Stainless rod that I machined out, its only designed to fire for about 2sec, to keep it below the melting point of SS as its not cooled and just long enough to ignite the main propellants and then shut off.It can take a fair bit of heat as you see in the video, SS melts at about 1500 Deg C so its getting fairly well up there for acouple of seconds but not long enough to do much if any damage........hopefully!

One of the things that gets demonstrated very nicely here is just one of the problems that has to be overcome when miniaturising engines, ie. thermal management. I know this is an igniter rather than a thruster, but it does show up what happens when the phsysics and temperatures stay the same but the radiative surface area decreases.

The injectors you're using look like they're from a Nox system - have you cannibalised a car? Looking forward to comparing engines!

Holy Cow! Way to go Iain! Hey, thay make a 2-stroke spark plug called a surface gap that you may like? An ingniter circut from a home heating unit (furnace) may provide a cheap soultion for a higher power long duration start? If your interested in some ideas? Good Work! Go Kiwi!